<!DOCTYPE html>
<html lang="en">

<head>
	<meta charset="UTF-8">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<title>Document</title>
	<script type="text/javascript">

		window.onload = function () {
			//分别为两个按钮绑定单击响应函数
			var btn01 = document.getElementById("btn01");
			var btn02 = document.getElementById("btn02");

			btn01.onclick = function () {
				alert(1);
			};

			btn02.onclick = function () {
				alert(2);
			};

			//设置btn01对鼠标按下相关的事件进行捕获
			//当调用一个元素的setCapture()方法以后，这个元素将会把下一次所有的鼠标按下相关的事件捕获到自身上
			btn01.setCapture();
		};

	</script>
</head>

<body>
	<button id="btn01">按钮01</button>
	<button id="btn02">按钮02</button>
</body>

</html>